FI119118B - A method for using a gas engine plant and a fuel feed system at a gas engine - Google Patents

Abstract

A gas engine plant that includes a combustion engine adapted to combust gaseous fuel receives fuel containing hydrocarbons, reforms the fuel by cracking the heavier hydrocarbons in the fuel while minimizing cracking of methane, and feeds the reformed fuel in gaseous form to the combustion engine.

Description

1 119118 METHOD FOR USING A GAS ENGINE FACILITY AND GAS ENGINE FUEL SUPPLY SYSTEM

The invention relates to a method for operating a gas engine plant according to the preamble of claim 1. The invention also relates to a gas engine fuel supply system according to the preamble of claim 8.

Crude natural gas is often the only possible fuel available for operating generators and compressor stations at remote sites and offshore platforms. In many cases, the amount of heavier hydrocarbons contained in the gas is not at an acceptable level. The use of such untreated gas in piston engines and gas turbines causes operational problems. The knock resistance of gaseous fuels 15 is often estimated by the methane number. In gas engines with a high compression ratio and thus a high thermal efficiency, the methane number is reduced due to the presence of heavy hydrocarbon components in the gaseous fuel. In many cases, gas engines running directly on the available gas fuel often are unable to produce the desired amount of power at gas drive 20 due to the low methane number of the gas mixture. If the gas engine is started to overload the power that is limited by the methane number • ·: '**, it will start knocking and power must be reduced.

• 1 · • ·: · Gas turbines also need to be used for gas determination and consideration •:: 25 in the design phase. If the gas turbine is designed for use eg.

• · · · · methane, the use of gas containing heavier hydrocarbons is problematic.

• · • · • · ·. Another state-of-the-art problem especially for oil rigs • · «

In connection with X1, it would be advantageous to use certain liquid fuels which are not currently available, such as gas condensates. It would be useful to be able to use the originally designed gas-powered engines, including liquid fuels such as gas condensate from the oil drilling process. Normally this is not possible without engine changes that cannot be made every time different types of fuel should be used.

5

It is an object of the invention to provide a method for operating a gas engine plant so that engine performance is maintained at a good level even with fuel containing heavier hydrocarbons, and to operate the gas engine even by utilizing liquid fuel. It is also an object of the invention to provide a gas engine fuel supply system that provides high methane fuel to the gas engine in a simple and easily controlled manner.

In the context of this specification, the term "gas engine" generally refers to an internal combustion engine powered by gas. The term "heavier hydrocarbons1" means hydrocarbons heavier than methane, CH4-

The objects of the invention are mainly achieved in the manner set forth in the appended claims 1 and 8 and described in more detail in the other claims.

According to the invention, a method of operating a gas engine plant comprising: an internal combustion engine adapted to burn gaseous fuel and a fuel supply system comprising a fuel source comprises at least: ·: 25 fuel heavier hydrocarbon digestion stages: gas; In this way, the quality of fuel supplied to the engine can be maintained at an acceptable level even though the fuel • · · *; ”1 initially contained heavy hydrocarbons.

The present invention also permits the use of heavier hydrocarbons containing 1,119,118 fuels, e.g., in a gas turbine designed to be used solely as methane fuel.

Cleavage reactions are preferably controlled by cleaving the heavier hydrocarbons in the fuel while minimizing methane cleavage. This can be accomplished by arranging for the amount of water dependent on the fuel composition and flow rate and the reforming unit to be present in the reactions, and maintaining the temperature of the reforming unit determined on a case-by-case basis in the reactor unit. In practice, the cleavage of heavier hydrocarbons 10 is mainly controlled by the temperature control of the reforming unit. Typically, the temperature of the reforming unit is maintained below 450 ° C.

It is still preferable that the fuel prior to the reforming unit is heated by transferring heat from the 15 fuels leaving the reforming unit.

According to a particular embodiment of the invention, the fuel source is a liquid fuel and the liquid fuel is vaporized by heat transferred from the fuel leaving the reformer unit before being fed to the reformer unit. By utilizing this embodiment:. a gas engine can also be run on an originally liquid fuel.

· 1 · • 1 ·

The gas engine fuel supply system of the invention comprises: • 1: a fuel source and a fuel source and gas engine connecting • ♦ ♦: 25 feed lines provided with a fuel reformer unit for the fuel ··· ♦. ·· ♦. to cut heavier hydrocarbons before feeding it into the engine.

«· ·. The supply line comprises the first supply line leading from the fuel source • · ♦ .1 ··. a reformer unit and a second feed line leading from the reformer unit to · 30 gas engines equipped with the first and second feed lines • · a common heat exchanger wherein • 1 ··· * ··· 4 119118 fuel is heated by transferring heat from the fuel in the second feed space. Preferably, the fuel reformer unit has a temperature control device that allows the temperature of the reformer unit to be maintained at a level that results in the cleavage of heavier hydrocarbons while minimizing the methane cleavage.

The actual operating parameters of the reforming unit are always determined by the gas used and the type of reformer used.

The invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which:

Figure 1 shows an embodiment of applying the fuel supply system of the invention in a gas engine plant, and Figure 15 shows another embodiment of applying the fuel supply system of the invention in a gas engine plant.

Figure 1 schematically illustrates a gas engine plant 1 having a fuel source 2 and a gas engine 3 and a fuel treatment unit 4. The gas engine may be, for example, a gas piston engine or a gas turbine. ... Both types of internal combustion engines are suitable for use in connection with the invention.

* lf • M · I · * • «

The fuel treatment unit 4 first comprises a filter element 5 which is «·; ... arranged from a fuel source 2 to a reformer unit 14 leading to a · · · * '. · * 25 first feed line 12. The filter unit 5 is arranged with particles and • · · "* ··". to separate other solid impurities from the fuel stream.

• ·

After the filter unit 5, the fuel flow direction is in the first. in supply line 12, pressure control valve 6. pressure control valve 6 adjusts * * ·, ···. fuel handling unit pressure, which is • · * 30 with the piston engine typically about 8 bar. Advantageously, valve 6 also has a safety shut-off valve built into it to close the valve outlet during possible malfunction of valve 6.

The first feed line 12 also has a shut-off valve 7 and a mouth valve 8 5 in a second feed line 13 for separating the fuel handling unit 4 from the system for special situations such as maintenance. The unit 4 is also pre-start and before maintenance can be commenced inert, which can be accomplished by means of a valve 10 and an inert gas inlet 9, here connected to the first feed line 12 after the shut-off valve 7. The inert gas may be e.g. nitrogen. The shut-off valves 7, 8 are, of course, closed before the start of maintenance work. The first and second feed lines may communicate with one another and bypass the processing unit 4 by means of a bypass channel 24. The bypass duct also has a shut-off valve 25.

Preferably, the unit also has a flow meter 11, for example, for adjusting the carbon vapor ratio of the process. Recirculation conduit 17 also has a second flow meter 15. Recirculation conduit 17 also has a high pressure pump 18 for spraying water to first supply line 12. Recirculation conduit 17 connects droplet separator 23 in second supply line 13 to first 20 supply line 12 after flow meter 11. The droplet separator is disposed in a second ... supply line 13 after a heat exchanger 19 connected to the first and * ·· j », second supply lines 12,13.

• «* 1 • ·:, ·. If the fuel is gaseous, the heat exchanger 19 is for heating the gas flowing in the first supply line "12" V 25 and in the second supply line 13 • »»] · 1 ·. for cooling the flowing gas. If the treatment unit 4 and the internal combustion engine 3 · · are initially operated with liquid fuel, the heat exchanger 19 will also be used. . ·. evaporates and heats the fuel in a gaseous state; and · · · ···. · 1 ·. simultaneously cooling the gas from the reformer unit 14 on the other side of the heat exchanger 19.

• · t • • • • • • 1 # • • · 6 119118

Further, the first feed line 12 has an auxiliary heater 20, e.g. an electric heater, for heating the gas to a suitable temperature prior to feeding it to the sulfur absorption unit 21 provided in the first feed line 12.Sulfur absorber may be required if the sulfur content of The operation of a steam reformer, a reformer in which hydrocarbons are reacted with water, is typically sensitive to the presence of sulfur. Here, the sulfur absorber communicates with reforming unit 14 via connection line 22. The connecting line in this case is also provided with an auxiliary heater 28. It should be noted that not all commercially available catalysts for the reformer unit need to be completely desulphurized.

The following describes the operation of the processing unit. Prior to start-up, unit 4 is rendered inert using nitrogen supplied through inlet 9 and 15 via valve 10. The shut-off valves 7 and 8 are closed and the vent valve 27 in the vent passage 26 is open. Nitrogen is passed through the system by opening valve 10. When all the oxygen has been flushed out of the system, the vent valve 27 is closed and the system is pressurized, e.g. as described below.

20

The recirculation fan 29 in the intermediate duct 30 connecting the first supply line 12 and the second supply line 13 is started and the valve 31 is opened.

By circulating nitrogen through the electric heater (s) 20, 28 in this manner. the processing unit 4 and the reforming unit 14 are heated to operating state.

• · · j1V 25 As the temperature rises, the pressure increases accordingly. When the operating mode is • · · "· '· [reached, the high pressure pump 18 is started to supply water * · to the nitrogen gas stream according to a pre-programmed C / S (carbon / vapor) ratio., ·, (Control equipment not shown). depends on the fuel composition «· 1, · 1” ·, and flow rate, and is determined in advance for each case • · 30. At least during start-up, water can be supplied to the unit e.g.

• · · through the water inlet (not shown) connected to the recirculation channel 17.

This also depends on the type of Reformation Unit used. When both the sulfur absorber and the reforming reactor have been flushed with moist nitrogen, the system is ready for use. During normal operation, the bypass channel 24 is closed by a shut-off valve 25.

5

When the fuel treatment unit 4 is in normal operation, the liquid fuel or heavy hydrocarbon containing gas from the fuel source 2 is first filtered in the filter unit 5. The fuel is then fed to a heat exchanger 19 where it is heated with reformed gas. If necessary, it is possible to add water to the fuel stream to achieve the desired carbon / vapor ratio in the reforming unit 14, e.g., through the auxiliary water inlet 32 guided by valve 33. If liquid fuel is used as a source, it is evaporated in the heat exchanger and further heated. The gaseous fuel, on the other hand, is heated, after the heat exchanger in the first feed line 12 15, to about 300 ° C, which is a suitable temperature for the sulfur removal unit 21.

Once the sulfur is removed from the gas, it is fed to reforming unit 14. In the reformer, reactions are controlled by maintaining a suitable temperature there. For this purpose, the reforming unit 14 is provided with a heater 37 which may be, for example, an electric heater. Operation of the heater 37 is based on a temperature measurement sensor 38 · ·: * ··· It is also possible to use an additional heater 28, t ·: V based on the temperature measurement sensor 38 connected to the reformer unit 14. It is important that the temperature remains at a level : 25 only results in the degradation of heavier hydrocarbons in the fuel • · • * · “j: while minimizing methane degradation. The appropriate temperature will depend on the actual catalyst used in the reforming unit 14 and the gas. of the composition.

• · • • • m m m m m m m m m m m m m 8 8 8 8 8 8 8 8 8 8 • • 119118

After the reforming unit 14, the gas is cooled and the moisture condensed in the downstream heat exchanger 19. The water droplets are separated and re-sprayed into the incoming gas stream.

If the reforming unit is of a type that requires hydrogen to be present in the reactions, a portion of the treated gas is recycled through the intermediate passage 30 and the circulating fan 29 to the first feed passage 12.

Figure 2 shows another embodiment in which the fuel supply system of the invention 10 is applied in a gas engine plant. It is much the same and has the same reference numerals as the embodiment shown in Figure 1, but has a different type of reforming unit 14. In this case, the reforming unit is a so-called reforming unit. autothermal Reformed (ATR), the adjustment of which in some cases offers benefits. The ATR type 15 reformer unit 14 has an air supply channel 34 provided with a control valve 35 which communicates with a source of pressurized air 36. In the ATR unit, it is possible to introduce the required water (vapor) into the splitting reactions by controlling the amount of air (or O2) supplied. By supplying air (or O 2), some of the gas is burned in reforming unit 14, producing heat and water (steam). This is useful because heavier hydrocarbons are typically the components that first react with oxygen in the air. In this way, both the steam addition and the temperature control of the reforming unit 14 in the ATR reformers can be achieved by the air supply • · · • · '\.

The invention is not limited to the above embodiments, but several variations thereof are conceivable within the scope of the appended claims. For example, other types of cracking equipment can be used instead of steam reformer. The reforming unit can be formed from a number of individual »« * units so that they can be used in various ways to provide suitable final gas properties.

* · · 1 »1 • · • · ··· • · · ·« «e ·· · * ·· ♦ * ·

Claims (10)

9119118 A method for operating a gas engine plant (1) comprising: 5 internal combustion engines (3) adapted to burn gaseous fuel and a fuel supply system comprising a fuel source (2), characterized in that the heavier hydrocarbons are chopped in the fuel feed sequence. (14) before feeding the fuel to the gas engine (3) while minimizing methane 10 degradation. Process according to Claim 1, characterized in that the digestion of the heavier hydrocarbons is controlled by the temperature control of the reforming unit (14). 15 Method according to Claim 2, characterized in that the temperature of the reforming unit (14) is kept below 450 ° C. Method according to one of the preceding claims, characterized in that the fuel is heated by transferring heat from the fuel leaving the reforming unit (14) before being fed to the reforming unit (14). The process according to claim 1, characterized in that the fuel source (2) is liquid fuel and that the liquid fuel is evaporated from the fuel leaving the reformer unit (14) by heat transferred. before being fed to the Reformation Unit (14). • • a • a • a at * A process according to any one of claims 1 to 5, characterized in that the water required for the cleavage reaction is supplied (32, 33) to the a **: * '30 fuel prior to the reforming unit (14). aa a a a a a a a a a a a a a a a a a a a a a a a a a 10 119118 A process according to any one of claims 1 to 5, characterized in that the water required for the cleavage reaction is produced in the reforming unit (14) through oxidation reactions of heavier hydrocarbons. A gas engine n (3) fuel supply system comprising a fuel source and a feed line (12, 13) connecting the fuel source (2) and the gas engine n (3), characterized in that the fuel line (12, 13) has a fuel reforming unit (14). ) fuel for the digestion of hydrocarbons heavier than methane before being injected into the engine (3). Fuel supply system according to claim 8, characterized in that the supply line comprises a first supply line (12) leading from the fuel source (2) to a reforming unit (14) and a second supply line (13) leading from the reforming unit (14) to a gas engine (3). and 15, the second supply line having a common heat exchanger (19) in which the fuel in the first supply line (12) is heated by transferring heat from the fuel in the second supply line (13). Fuel supply system according to claim 9, characterized in that the fuel reforming unit (14) has a temperature control device (38). • • · t t t ♦ · tt tt tt 9 9 9 9 9 9 9,999 9 9 9 9 999 9 9 9 9 9 9 9 • 99 999 9 9 9 9 • 99 9 • 9 9 9 9 9 9 9 9 9 • 99 • 9 9 9 • 99 9 9 999 • 9999 9 9 9 119118